Arid4a−/−Arid4b+/− male mice displayed defects in male reproductive function. (A and B) Progressive loss of fertility in the Arid4a−/−Arid4b+/− male mice. Percentages of fertile males (A) and litter size (number of pups) (B) were compared between wild-type and the Arid4a−/−Arid4b+/− male mice from 2 mo of age through 1 y of age. (C) Hypogonadism and seminal vesicle agenesis/hypodysplasia in the Arid4a−/−Arid4b+/− male mice. Morphology of the whole male reproductive system (Top), seminal vesicles (Middle), and testes (Bottom) was compared between wild-type and Arid4a−/−Arid4b+/− mice. (D) Testis weight (a), body weight (b), and testis weight normalized against body weight (c) were shown from wild type and the Arid4a−/−Arid4b+/− mice at 2 and 10 mo of age. Horizontal lines indicate the means. Wild type, 2 mo (“2m”) old—4 males and 10 mo old—6 males; fertile Arid4a−/−Arid4b+/−, 2 mo old—6 males and 10 mo old—6 males; infertile Arid4a−/−Arid4b+/−, 2 mo old—3 males and 10 mo old—8 males.